On the time-dependent reversible stochastic compartmental model—II. A class ofn-compartment systems

This paper discusses the solution of a generaln-compartment system with time dependent transition probabilities utilizing the technique described by Cardenas and Matis (1975) (hereafter abbreviated (CM)). In addition, the cumulant generating function is derived for a special class of reversiblen-compartment systems where the time-dependent intensity coefficients corresponding to the migration and death rates are some multiple of each other. The immigration rates can be any integrable function of time. The moments are also obtained and the solution to the two-compartment system is presented explicitly. The solution is illustrated with a linear and a periodic function which forms have been widely reported in the literature.     

Farm background,socioeconomic status,and fertility: The two‐generation hypothesis

Abstract

This paper reports on an examination of whether the effects of farm background on socioeconomic differentials in fertility are diminished among nonfarm couples. The data are for a sample of white ever‐married women belonging to the 1901–1910 birth cohorts. The research provides another test of the two‐generation‐urbanite hypothesis first advanced by Goldberg. Unlike a number of other studies, the findings do not support the hypothesis. Reasons for the lack of support are discussed, and methodological weaknesses of previous studies are identified.     

The exclusive economic zone and antarctica: The dilemmas of non‐sovereign jurisdiction

Abstract

Antarctica is the only continent from which no exclusive economic zones extend. This article examines the EEZ as a legal concept, particularly its relevance for enhancing maritime jurisdiction offshore Antarctica. The study analyzes the political setting in the Antarctic which would affect creation of EEZs in the region, especially the division of the continent into sector claims by certain states and the implications presented by various island groups in the area. An appraisal is made of the legal situation and the jurisdictional opportunities afforded by the Antarctic Treaty System. The author concludes that a recognized political authority, with demonstrated legal competence and capabilities, is administering jurisdictional considerations in the Antarctic area. In its operation, this Antarctic Treaty regime fulfills management and conservation functions analogous to those of EEZs in waters offshore the continent.     

On the time-dependent reversible stochastic compartmental model—I. The general two-compartment system

The distribution of the two-compartment, reversible system with time-dependent transitions is proposed and verified. Inasmuch as the required probabilities cannot, in general, be expressed in closed form, a method of approximating these probabilities is described. An example with specific inverse functions of time is presented.     

The state,housing policy and Afro‐Caribbean migration to France

France's Afro‐Caribbean population forms a distinctive element in postwar migrant labour recruitment: of French nationality, with an equal balance of men and women, and strongly concentrated in public sector employment, especially in the Paris region. State policy strongly influenced the migration flow from the Caribbean islands, especially from the early 1960s. This article looks at aspects of the migrants’ housing experience, using aggregate statistics to establish general tenure patterns and interviews to recreate biographical histories. Afro‐Caribbean migrants avoided for the most part the worst excesses of the housing crisis of the 1960s and 1970s, though housing conditions ‐ especially for newly‐arriving migrants ‐ were frequently poor. Access to the public housing sector is shown to be crucial, though the role of the state was less direct (specifically aimed at the Caribbean population through the migration agency) than indirect (through the role of employers and the general involvement of the state in housing provision).     

The third United Nations conference on the law of the sea and non‐independent states

Abstract

The Third United Nations Conference on the Law of the Sea is addressing problems that involve all of mankind. Yet there are parts of mankind, non‐independent states and special sovereignties, that are not directly represented at the conference, even though their interests will be directly affected by the decisions taken.

There currently arc around 75 non‐independent states and special sovereignties at different stages of political development and with varying forms of association to a metropolitan power. This can create problems of conflicting jurisdiction over ocean space in two areas particularily: the South Pacific and the Caribbean.

The Conference has attempted”; to deal with the problem of the Law of the Sea and non‐independent states in three ways: by granting observer status to national liberation movements and associated states; through the Transitional Provision; and through the Definitional and Final Clauses. However, a universal formula that would guarantee to these states the resource rights recognized in the proposed Treaty has yet to emerge.     

Interpretation of nonlinear steady state enzyme kinetics—Cyclic and mathematical properties of cooperative,second-site and random pathway models

Nonlinear steady state kinetic patterns are frequently encountered in enzyme studies. Consequently, there is a need to develop procedures for systematically interpreting such data. This paper contributes to this development by identifying a common feature in nonlinear systems and by showing that quite different models commonly in use give very similar mathematical functions.Identical or similar cycles can result from quite different chemical events in enzyme mechanisms, cooperativity, second sites and random pathways. Such cycles can account for many of the observed nonlinear patterns, i.e., power functions, substrate activation and inhibition. Therefore nonlinear steady state kinetics generally requires the presence of a cycle(s) in the mechanism without specifying the underlying chemical events giving rise to that cycle(s).Rate equations for cooperative, second-site and random pathway models are derived and shown to yield virtually identical mathematical functions. Thus empirical equations composed of these functions can be used to represent nonlinear kinetic data without specifying the underlying chemical events.     

Estimation of bird distribution based on ring re‐encounters: precision and bias of the division coefficient and its relation to multi‐state models

Capsule The division coefficient is an estimate of the proportion of ringed birds migrating to different destination areas taking into account area‐specific re‐encounter probabilities.

Aims To explore precision and bias of the division coefficient method by a simulation study and to compare the approach with multi‐state models.

Methods In a simulation study true and estimated division coefficients were compared. The division coefficient method was mathematically compared with the multi‐state model.

Results The estimated division coefficients seemed to be unbiased if the assumptions were met. The precision decreased if the bird distribution became similar in both bird groups and when difference between area‐specific re‐encounter probabilities increased. A bootstrap method to assess precision is presented. The estimates from the division coefficient method equal the maximum likelihood estimates in a multi‐state model including only one time interval.

Conclusion Before applying the division coefficient method or a multi‐state model to real data a simulation study should be conducted in order to explore the behaviour of parameter estimation. The division coefficient method with the bootstrap confidence intervals is an easy alternative to a multi‐state model with one time interval when the bird distribution between destination areas (e.g. migratory connectivity) alone is of interest.     

Factors influencing the phytoplankton steady state assemblages in a drinking-water reservoir (Ömerli reservoir, Istanbul)

In situ growth of heterotrophic nanoflagellates (HNF) in Lake Donghu, a eutrophic shallow lake in mainland China, was studied from January 1999 to March 2000 using a modified Weisse protocol. The study results indicated that the growth rates of HNF showed pronounced seasonal variation (–0.37–1.25 d^–1), reaching the maximum during spring to early summer. When the water temperature was higher than 25.5°C, HNF growth was inversely proportional to water temperature. There was an effect by bacterial abundance and autotrophic picoplankton on HNF growth that depended on location. HNF biomass was the highest in late spring, and the HNF production ranged from –2.25 to 35.45 mg l^–1 d^–1 with mean of 3.17 mg l^–1d^–1. When considered in the context of biomass and production data for zooplankton in Lake Donghu, it was evident that HNF contributed significantly to the total zooplankton production in Lake Donghu. These in situ studies indicate that temperature and food supply are the major determinants of HNF abundance and productivity.     

Masting,mixtures and modes: are two models better than one?

A key hypothesis in population ecology is that synchronous and intermittent seed production, known as mast seeding, is driven by the alternating allocation of carbohydrates and mineral nutrients between growth and reproduction in different years, i.e. ‘resource switching’. Such behaviour may ultimately generate bimodal distributions of long‐term flower and seed production, and evidence of these patterns has been taken to support the resource switching hypothesis. Here, we show how a widely‐used statistical test of bimodality applied by many studies in different ecological contexts may fail to reject the null hypothesis that focal probability distributions are unimodal. Using data from five tussock grass species in South Island, New Zealand, we find clear evidence of bimodality only when flowering patterns are analyzed with probabilistic mixture models. Mixture models provide a theory oriented framework for testing hypotheses of mast seeding patterns, enabling the different responses underlying medium‐ and high‐ versus non‐ and low‐flowering years to be modelled more realistically by associating these with distinct probability distributions. Coupling theoretical expectations with more rigorous statistical approaches will empower ecologists to reject null hypotheses more often.     

Trypanosoma cruzi: two genetic groups in Paraná state, Southern Brazil

This paper presents the genetic characterization of Trypanosoma cruzi strains isolated from chronic chagasic patients, triatomines, and sylvatic reservoirs from Paraná state, Southern Brazil, using the RAPD and SSR-PCR techniques. It has shown the presence of both phylogenetic groups of T. cruzi (I and II), describing for the first time the existence of T. cruzi II in Paraná state.